This invention relates to gimballing arrangements. It may, for example, be used for scanning and tracking antennas and the like. The present invention provides a biaxial (biax) gimbal mounting arrangement permitting both axes of rotation to intersect at a point within the load being gimballed.
Gimbal mounts are widely utilized for, among other things, antennas and optical transducers. For many applications, it is desirable to scan the antenna or transducer in a predetermined manner so as to monitor a predetermined sector of space. In other applications it is desirable to track a target. As the target moves, the antenna or optical transducer must be moved so as to maintain the target within a narrow beam of the antenna or optical transducer being gimballed. The patent literature is replete with various types of arrangements for gimballing antennas. The following is merely a small sample of the patent literature and is not intended to be an exhaustive list.
U.S. Pat. No. 1,932,469--Leib et al (1933) PA1 U.S. Pat. No. 2,512,636--Flynt (1950) PA1 U.S. Pat. No. 2,700,106--Taylor (1955) PA1 U.S. Pat. No. 2,740,962--Hammond, Jr. (1956) PA1 U.S. Pat. No. 2,924,824--Lancott et al (1960) PA1 U.S. Pat. No. 3,987,452--Godet (1976) PA1 U.S. Pat. No. 4,020,491--Bieser et al (1977) PA1 U.S. Pat. No. 4,238,802--Speicher (1980)
Of the patents listed above, the Leib et al U.S. Pat. No. 1,932,469, Flynt U.S. Pat. No. 2,512,636, Taylor U.S. Pat. No. 2,700,106, Lancott et al U.S. Pat. No. 2,924,824 and Bieser et al U.S. Pat. No. 4,020,491 all disclose gimballing arrangements that have the inherent capability to rotate an attached load about its center of gravity. However, significant amounts of extraneous mechanism must be provided in order to accomplish this result. This may increase power requirements typically necessary to carry out a high speed scan. These patents teach azimuth-elevation or conical scan gimbals vis-a-vis the biax scan gimbal arrangement described herein. Conical scan gimbals have significant drawbacks compared with biax scan gimbals.
Conical scan gimbals rotate their load about its line of sight in the process of pointing the load toward a target. This may sometimes preclude the use of a polarized antenna, such as a radar antenna or a polarized optical sensor or an imagine sensor. In addition, conical scan gimbals may be unsuitable for very sensitive simple monopulse radar techniques in which an antenna is constructed to provide left-right, up-down error signals in an acquisition track mode of operation.
The Hammond U.S. Pat. No. 2,740,962 and Speicher U.S. Pat. No. 4,238,802 patents disclose biax gimbals that rotate a load about its center of gravity. However, in both cases, the load, i.e., the antenna, is small enough to fit in a cage or is counter balanced. The Hammond, Jr. U.S. Pat. No. 2,740,962 arrangement requires a rather large envelope and the Speicher U.S. Pat. No. 4,238,802 arrangement appears structurally compliant and weak. Both move significant amounts of mechanism along with the load.
The Godet U.S. Pat. No. 3,987,452 arrangement discloses a rather complex biax gimbal. However, it may have a high inertial load and vibration sensitivity due to the swinging action that is produced in pointing.